Hiccup might be very resistant at first. He's always been an independent thinker, so being forced into a marriage would go against his nature. He could try to find ways to escape the situation, like running away or finding loopholes in the marriage contract. But as he spends more time with Astrid, he might start to see her in a different light and become more accepting of the situation.
Well, Bakugo might scoff at first. He'd probably think Batman is too brooding and not as straightforward as he likes his heroes. But then as he reads more of the fanfiction, he might grudgingly admit that Batman's detective skills are cool. Deku, on the other hand, would be super interested. He'd be analyzing every move Batman makes in the fanfiction, taking notes in his head about Batman's strategies and how they could be applied in his own hero work. Uraraka would be more focused on the relationships in the fanfiction. She'd be all 'aww' at the cute moments and feel for the characters when they're in trouble.
He would probably be shocked at first. Just imagine seeing an older version of yourself. He might be a bit skeptical too, thinking it could be some kind of trick.
The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.
Well, obviously Deku in two forms - the younger and the older version are the main characters. The younger Deku is the one who is still growing and learning, while the older Deku has more experience.
Another plot might involve the older Deku being from an alternate timeline. He shows the younger Deku different ways he could have developed his skills and relationships, which makes the younger Deku reevaluate his own path as a hero.
As of now, Deku is very much alive in the manga. The plot hasn't reached a point where he meets such a fate. Usually, main characters like Deku have significant story arcs and aren't easily killed off.
Several characters have met their demise in the MHA manga, but it's a bit complex to list them all precisely. Some of the notable ones include [mention specific characters if known].